We studied the interactions between wild black and gold howler monkeys (Alouatta caraya) and other mammals at three sites with different human disturbance levels and for-est structures in northeastern Argentina. The main goal was to
evaluate the effects of the study site and type of interaction (agonistic or non-agonistic) on the rate of interaction. In addi-tion, we also described the associations between interspecific interaction rate, species involved, howler monkeys’ activity, and seasonality. We present 50 group-years for 14 groups, collected between 2003 and 2012. We registered a total of 29 interactions (0.22 ± 0.26 interactions/100 h). Most interac-tions (56.7%) were agonistic (12% of high intensity and 88% of low intensity), 41.9% were neutral, and 1.5% were affiliative. We found that both factors, site and type of inter-action, have an effect on the rate of interaction. Interspecific interactions were more frequent at the two sites without hu-man settlement than in the rural site. Interspecific interactions occurred during resting (46.73%), traveling (27.40%), and feeding (25.87%). Interactions occurred throughout the year but were concentrated in August (late winter) and September (beginning of spring). Our results suggest that both site and type of interaction affected the rate of interaction between howler monkeys and other mammals in northeastern Argentina. Agonistic interactions were more frequent that non-agonistic ones, and monkeys reacted agonistically to sev-eral mammalian species, but these interactions were mainly of low intensity.